On e621.net is discussed by the users in the forum and then decided whether an alias is changed or set. There was some time ago, for months, a discussion about Cuntboy and Dickgirl, who should get new names. Here I guess the admin decides.
If I'm not mistaken, alias work like this. Titis, boob, breasts, ...... no matter what word you use in the search, the search probably shows you breasts, since they are fused together in the word since they have the same meaning. They should simplify things and in e621 "Cuntboy" they should replace abusive words. Can not guarantee that it is so.